1. Field
The present disclosure relates in general to vehicle refueling systems, and more particularly to vehicle refueling systems capable of providing air or vapor to the filler nozzle during refueling operations.
2. Description of Related Art
Refueling systems for vehicles designed to reduce emission of fuel vapors during refueling operations are generally well known. Many of these systems employ filler nozzles that require a supply of make-up air, or vapor, to continue delivering fuel, and that automatically shut off when the make-up air supply is cut off or reduced below a minimum level. As used herein, the term “air” shall be understood to refer to both air from the external atmosphere, and to air including a vaporized fuel component, commonly referred to as “vapor.” Make-up air is typically supplied by a re-circulation line from the fuel tank. One example of such a refueling system is disclosed in U.S. Pat. No. 5,950,655, entitled “MECHANICAL SEAL ORVR SYSTEM AND CONTROL VALVE,”, issued Sep. 14, 1999, referred to hereinafter as the '655 patent. The '655 patent is commonly owned by the assignee hereof, and is fully incorporated by reference herein, as though set forth in full, for its teachings on refueling systems.
In refueling systems such as those described in the '655 patent, a mechanical seal is included in the filler pipe cup that seals to the filler nozzle during refueling operations. This significantly reduces vapor generation during refueling by blocking air from entering the filler pipe and mixing with the fuel being dispensed. This, in turn, reduces the vapor loading presented to the charcoal canister of the fuel system during refueling.
Because the filler nozzles require the presence of make-up air in order to continue dispensing fuel, a vehicle refueling system including a mechanical seal in the filler cup must provide a means for providing make-up air. As noted above, this is typically provided via a re-circulation path from the fuel tank to the filler pipe cup region. The re-circulation path may be designed so that make-up air is provided until the tank is full, at which point the re-circulation path closes, and the fuel dispensing operation is shut down by the filler nozzle due to the lack of make-up air.
It is desirable that the re-circulation path include an air-flow restriction such that the filler pipe cup region maintains a small negative pressure relative to atmospheric pressure and thereby promotes capture of fuel vapors within the vehicle fuel system. However, difficulties can occur when Vapor Vac™ [“Vapor Vac” is a registered trademark of Gilbarco, Inc.] style refueling pumps are used with such a system. Vapor Vac™ style pumps are used in several areas within the United States. Because Vapor Vac™ pumps are designed to perform all of the vapor recovery during operation by pulling vapors into the end of the filler nozzle, a re-circulation path may be unable to provide sufficient make-up air to prevent the filler nozzle from shutting off. In such a scenario, the vehicle's refueling system should provide an additional supply of make-up air. The present disclosure teaches a novel and advantageous system that addresses this need.